Various kinds of biaxial stretch blow molding apparatus for manufacturing blow-molded products such as PET bottles are known, and such apparatuses fundamentally include a preform supplying station, a heating station for heating preforms, a blow station equipped with blow-molding molds that biaxially stretch the heated preforms by blowing, and a collection station that collects blow-molded products from the blow-molding mold. One example of such a biaxial stretch blow molding apparatus of this construction has been proposed by the present applicant in Reference Document 1 indicated below. A rotary-type device where a plurality of blow-molding molds are mounted on a turntable at intervals of a fixed angle is also known as the blow station.
In the blow molding apparatus of this construction, a large number of preforms can be heated efficiently and apparatus size can be reduced by transporting the preforms with a narrow feed pitch within the heating station. When the preforms are transferred from the heating station to the blow station after heating, it is necessary to increase the feed pitch so as to match the feed pitch of the blow-molding molds. As disclosed in Reference Document 2 indicated below, as one example of a mechanism for transporting the preforms while increasing the feed pitch, a mechanism in which preforms that are transported along a circular transportation passage with a narrow feed pitch are gripped by gripper devices transported along a separate circular transportation passage with a large feed pitch is known. The gripper devices are each held by a swing mechanism that swings the gripper device in a lateral direction and a linear movement device that linearly moves the gripper device in a anteroposterior direction, and are constructed so that when preforms are received, the respective gripper devices are transported while receiving the preforms so as to have the same feed pitch as the preforms transported with the narrow feed pitch in this movement mechanism.
The preforms are transported via the heating station and the blow station while being held with an inverted posture on carriers. Normally, preforms supplied from the preform supplying station with an upright posture are inverted, mandrels are inserted into opening parts of the preforms from below, and the preforms are thereafter transported in this state. After blow-molding has been carried out by the blow-molding molds to produce blow-molded products, the mandrels are withdrawn downward from the opening parts of the blow-molded products, and then the blow-molded products are inverted and collected in the collection station. A mechanism for inverting and placing performs in the carriers is also disclosed in Reference Document 2 indicated below.
As the blow-molding mold, a construction that opens and closes a left/right pair of molding dies in the lateral direction to open and close the mold is known. As a mold opening mechanism for the blow-molding mold of this construction, devices that use a link mechanism are disclosed in Reference Documents 3 and 4 indicated below, for example.    Reference Document 1: JP-A 2000-117821    Reference Document 2: JP-A 11-115039    Reference Document 3: JP-A 6-15724    Reference Document 4: JP-A 6-39909
In the transfer mechanisms for changing the pitch described above, the gripper devices are positioned by a combined movement of swing movement by the swing mechanism and linear movement by the linear transfer mechanism. However, to position the gripper devices at a receiving position and a transfer position of the preforms using such combined movement, component parts of the respective mechanisms need to be precisely manufactured and also precisely assembled. Accordingly, there is the problem that manufacturing is difficult and the manufacturing cost is high.
In addition, when preforms and blow-molded products are transferred between circular transportation passages, the gripper devices should preferably face one another on both sides in a radial direction of the transportation passages. However, in conventional mechanisms, the gripper devices are oriented toward the radial direction only at the moment when the preforms and the like are transferred. This means that there is the risk that it will not be possible to transfer the preforms and the like reliably.
Also, the conventional blow molding apparatus requires separate turntables for carrying out operations that invert the preforms, invert the blow-molded products, insert mandrels into the performs, and withdraw the mandrels from the blow-molded products. As described above, a mechanism that changes the feed pitch of the preforms and also inverts the preforms has been proposed, but fundamentally four turntables are required, so that there is the problem that the dimensions of the machine increase, as does the manufacturing cost.
In the mold opening/closing mechanism for blow-molding molds that can open and close laterally in the conventional blow molding apparatus, the link mechanism comprising the mold opening/closing mechanism extends from rear surfaces of the respective blow-molding molds in a planar direction toward a center of the turntable that rotates the respective blow-molding molds. Here, a large number of heavy blow-molding molds are mounted on the turntable and the transporting of the respective blow-molding molds needs to be carried out precisely. Accordingly, it is preferable for bearing members that rotatably supports the turntable to be disposed as close as possible to a position directly below heavy objects, that is, directly below the blow-molding molds on the turntable. However, since the conventional mold opening/closing mechanism is elongated in the planar direction toward the center of rotation of the turntable from the respective blow-molding molds, there is the problem that in order to avoid interference with the mold opening/closing mechanism, the bearing members have to be positioned close to the center of rotation of the turntable.